This invention pertains to the art of handles and more particularly to operating handles.
The invention is particularly applicable to a two piece safety handle and will be described with particular reference to its use on a ball valve; however, it will be appreciated by those skilled in the art that the invention has broader applications and may be advantageously employed in any number of different environments which require operating handles.
Ball valves have traditionally employed what may be termed as lever handles. These handles are simple to make, easy to turn and clearly define the off-on positions of the valve. However, in some installations such as chemical plants, there has been a fear of accidents caused by someone catching his clothing on a valve handle and inadvertently actuating it. Such accidents can substantially upset or even cause an entire shut-down in plant operations as well as subject plant personnel who may be working on an opened system downstream from the valve to serious injury. To overcome these problems, safety handles have been variously required by safety legislative and/or enforcement agencies. Such safety handles are required to be round or oval with all corners well rounded so that a sleeve or similar article of clothing will slip off the handle rather than catch thereon. In addition, safety handles must also include some means of showing valve position, that is, valve opened and closed positions.
Various types and designs of prior safety and conventional handles have been of a one-piece construction and included a mounting opening or hole therethrough in order that the handle could be conveniently mounted to a valve operating stem. Some prior valves have included opposed flats adjacent the outermost end of the stem for purposes of closely receiving a handle and for preventing a loose or sloppy fit between the stem and handle. With prior handles, it has been necessary to maintain the hole size tolerances very close to the stem flat width. Even with extremely close tolerances, however, there is still some clearance between the hole and the stem. Thus, after a few cycles of operation, the corners of the stem flats become rounded so that there was noticeable slop in the handle-stem fit. Such arrangements are extremely undesirable in valving situations.